On Tuesday, during his 21-hour marathon "filibuster" against Obamacare, he read aloud to his daughters back home the Dr. Seuss book "Green Eggs and Ham." But he clearly missed its message.

In the Seuss tale, Sam-I-Am, a lover of green eggs and ham, tries to persuade a friend to try them. But the man resists. He resists so persistently and so adamantly that he ends up sounding a lot like the Republicans on Capitol Hill who are determined to defund President Obama's healthcare law. But in the Seuss story, the man is finally persuaded to try the offending eggs and ham, and, much to his surprise, he loves them.

If only the GOP would take a page from that book.

In fact, the GOP could do a lot worse in its choices for filibuster reading material than Dr. Seuss books. Theodor Geisel, who adopted the pen name Dr. Seuss, was an outspoken progressive who actually has a lot to teach today's Republicans.

In the early 1940s, before he became the world's bestselling children's author, Geisel was an editorial cartoonist for PM, a fervently liberal pro-New Deal daily newspaper in New York that devoted sections to unions, women's issues and civil rights. The tabloid paper "was against people who pushed other people around," Geisel explained. "I liked that."

His cartoons viciously but humorously attacked Adolf Hitler and Benito Mussolini. He bluntly criticized isolationists who opposed America entering World War II, especially famed aviator (and Hitler booster) Charles Lindbergh and right-wing radio priest Father Charles Coughlin, both of whom were anti-Semites. He used his cartoons to challenge racism against Jews and blacks, union-busting and corporate greed, which he thought divided the country and hurt the war effort. He decried the U.S. military's racial segregation policies.

In 1947, Geisel lampooned anti-communist hysteria with a drawing in the New Republic that showed Uncle Sam looking on in horror at Americans accusing one another of being communists.

In his children's books, Geisel was often a moralist, and his politically progressive views suffuse his stories. His books use ridicule, satire, wordplay and wild drawings to take aim at bullies, hypocrites and demagogues. Many Dr. Seuss books are about the misuse of authority — by despots, kings or even parents. In a university lecture in 1947, a decade before the modern civil rights movement, Geisel urged would-be writers to avoid the racist stereotypes common in children's books, noting that America "preaches equality but doesn't always practice it."

So go for it, GOP. Embrace Dr. Seuss as the go-to author for future filibusters. Here are some ideas to get you started:

"Horton Hears a Who!" (1954). This book, written during the McCarthy era, features Horton the Elephant, who befriends tiny creatures (the Whos) whom he cannot see but can hear thanks to his large ears. In the book, Horton rallies his neighbors to protect the endangered Who community. As Horton puts it:

"A person's a person, no matter how small."

"Yertle the Turtle" (1958). In this book, Yertle, king of the pond, stacks up his subjects and stands on top of them in his attempt to reach higher than the moon. Mack, the turtle at the bottom of the pile, finally protests:

"I don't like to complain,

"But down here below, we are feeling great pain.

"I know, up on top you are seeing great sights,

"But down at the bottom we, too, should have rights."

The Sneetches (1961). In this book, a condemnation of bigotry, some of the yellow birdlike creatures known as Sneetches have green stars on their bellies. They look down on the Sneetches without them. After the starless Sneetches pay a huckster to put stars on their bellies, the original ones with stars pay the same huckster to take theirs off. Eventually, after several rounds of star addition and removal, the Sneetches realize the absurdity of judging someone by appearance.

The Lorax (1971). This cautionary tale about pollution came out less than a year after the environmental movement held its first Earth Day celebration. In it, a man tells a young boy the story of how the area lost its lovely Truffula trees and bearlike Bar-ba-loots despite the best efforts of the Lorax, who "speaks for the trees." His warnings are ignored by the factory owner who insists:

"Business is business!

"And business must grow."

It would be hard even for Sen. Cruz to miss Geisel's point.

Peter Dreier teaches politics and chairs the Urban & Environmental Policy Department at Occidental College. His latest book is "The 100 Greatest Americans of the 20th Century: A Social Justice Hall of Fame."